1. Field of the Invention
The present invention relates generally to methods and apparatus for extracting fetuses from the mother to facilitate delivery. The present invention relates more specifically to apparatus and methods for vacuum assisted fetal extraction and the monitoring of an applied vacuum used in such a procedure.
2. State of the Art
During childbirth, the birth mother often requires assistance in the delivery of the fetus. In certain, more extreme instances, such assistance may include surgical intervention known as a Caesarean section delivery. A Caesarean delivery involves making an incision in the abdomen and uterus and extracting the fetus through the incisions. In less extreme cases, assistance is provided through the use of various extraction tools or instruments. Typically, such instruments include either forceps or a vacuum cup device, either of which is used to grip the fetus"" head to maneuver the fetus through the birth canal.
The use of forceps entails grasping and compressing the fetus"" head between a pair of opposable members at the distal end of a scissors-like instrument and then maneuvering the fetus"" head with the forceps. While the use of forceps allows for considerable manipulation of the fetus, the rigid instrument and force applied to the head by the physician""s gripping of the proximal ends of the forceps to maintain secure contact with the fetus"" head are potentially damaging to the soft and pliable head. Harm may also inadvertently come to the mother""s body during manipulation of the fetus due to the unyielding nature of the forceps.
Vacuum assisted extraction devices comprise well known alternatives to forceps. Vacuum assisted fetal extractors, sometimes referred to in their simplest manifestation as obstetric vacuum cups, may be utilized in order to apply an externally created vacuum force to the head of the fetus to secure the extractor to the head for use as a traction device. Vacuum cups generally operate by placing the cup on the head of the fetus, mechanically evacuating air from the cup and simultaneously drawing the cup against a portion of the fetus"" head. By so attaching the cup to the fetus"" head, a traction force may be applied to the fetus such that it may be manipulated and the fetus pulled from within the mother""s uterus in conjunction with the mother""s contractions.
While vacuum assisted fetal extractors have provided many advantages in the delivery of a fetus from its mother, such devices also pose potential hazards if not properly utilized or adequately monitored during their use. Such hazards stem from the fact that the fetus"" skull is soft and structurally weak and thus renders the head of the fetus susceptible to deformation or injury during childbirth.
Misapplication or improper use of a vacuum assisted fetal extractor may result in any of a number of injuries to the fetus. Such injuries might include, by way of example only, subdural hematoma, subgaleal hemorrhage, chignon, abrasions, as well as other, less common injuries. While not an exhaustive list, injuries of the foregoing type listed above may be the result of improper placement of the vacuum cup on the fetus"" head, application of an excessive vacuum magnitude, or maintaining a vacuum for an excessive continuous duration. Injury may also occur as a result of maintaining a vacuum for an excessive cumulative duration either during a specified period of time (e.g., longer than 20-30 minutes) or as a total cumulative duration.
Additionally, the occurrence of one of the above-listed potentially injurious events may influence or magnify the effects of another. For example, the application of a vacuum of a greater magnitude may affect the maximum desirable duration of the applied vacuum, either for application over a fixed, specific period or for a cumulative duration.
Thus, it would be desirable to provide, in the art of vacuum assisted fetal extraction, a technique for monitoring the application of a vacuum force to a fetus"" head to avoid or ameliorate potentially undesirable effects of the vacuum on the fetus. Such monitoring technique would preferably be effectuated through use of a device which is simple and reliable in design and in operation, adaptable to existing vacuum-type extraction devices, conducive to long-term storage and inexpensive to fabricate so as to enable its disposal after a single use.
Additionally, it would be advantageous to include with such monitoring technique the use of a representative, preferably automated index or scale resulting from a combination of multiple, potentially harmful factors or parameters attendant to vacuum assisted delivery such that monitoring of such multiple factors or parameters during a procedure is simplified.
In accordance with one aspect of the invention, a monitoring device is provided for use with vacuum assisted fetal extractors. The monitoring device includes a circuit configured to provide, at least in part, a timing function or timer. An output unit such as, for example, a liquid crystal display (LCD) is operably coupled to the circuit to receive a signal from the circuit which is indicative of one or more durations as measured by the timer. A switch is also operably coupled to the circuit and to a vacuum reservoir such that creation of a vacuum in the vacuum reservoir by a vacuum source to be communicated to a cup or other structure used to form a vacuum chamber with the fetus"" head to grip the head actuates the switch and activates the timer. Full or partial (as by relaxation of the vacuum below a selected threshold) release of the vacuum in the vacuum reservoir likewise releases the switch such that the timer is deactivated. The output unit may display or record duration of an applied vacuum, or both display and record same. The monitoring device and output unit may include additional features such as a pressure (vacuum) sensor operably coupled to the circuit and output unit to enable displaying and/or recording the magnitude of vacuum being applied in either continuously or in terms of peak figures. The pressure sensor may be used in lieu of the switch to activate and deactivate the timer at the same or different levels of pressure or vacuum. The monitoring device may be configured to time the duration of a specific application of vacuum or to time on a cumulative basis to sum the durations of multiple applications of the vacuum. Furthermore, if the monitoring device is configured to time duration of vacuum application on a cumulative basis, the cumulation may represent an absolute cumulative total for all applications of the vacuum, or it may represent a cumulative duration of vacuum applications within a specified rolling time period such as, for example, the immediately preceding hour. The monitoring device may also be configured to record and keep track of the number of times a vacuum is generated and released, as well as the number of times traction is applied to the infant. Application of traction may be indicated through, for example, detection of fluctuations in vacuum level as the infant is pulled, by the number of vacuum increase/decrease cycles detected, or through use of a force sensor. The circuit may further include one or more alarms responsive to the timing function or the pressure sensor to alert the clinician as to when a vacuum duration or magnitude has been, or is about to be, exceeded.
In accordance with another aspect of the present invention, a second embodiment of a monitoring device is provided for use with vacuum assisted fetal extractors. The second embodiment may be configured as described above with respect to the first embodiment. However, in the second embodiment, the output unit, such as, for example, an LCD, may be operably coupled to the circuit to receive a signal from a processor associated with the circuit which is indicative of a transfer function representative of an index or scale indicative of the combined effects on the fetus"" head of, for example, at least a magnitude or magnitudes of the applied vacuum as measured by the pressure sensor and the duration or some cumulative durations of the applied vacuum as measured by the timer. The output unit may also display or record the durations, as well as magnitudes, of the applied vacuum.
In accordance with another aspect of the present invention, a vacuum assisted fetal extraction apparatus is provided. The vacuum assisted fetal extraction apparatus includes a vacuum cup or other structure configured to be applied to the head of a fetus to form a chamber therewith and a vacuum source operably coupled to the vacuum cup to selectively create a vacuum when the cup is placed against the fetus"" head. The vacuum assisted fetal extraction apparatus also includes a monitoring device similar to one of those described above.
In accordance with yet another aspect of the invention, a method is provided for using a vacuum assisted fetal extraction apparatus. The method may include applying a vacuum one or more times to secure the apparatus to a portion of the fetus, measuring the magnitudes of A the vacuum as applied and communicating the measurements to the clinician. The duration or durations of the applied vacuum may also be measured and then communicated to the clinician. The method may also include measuring both magnitude and duration of vacuum application, as well as clocking total duration and number of multiple vacuum applications either absolutely or within a defined time frame. The method may further include alerting an operator with an audible or visible alarm when a measured value has been or is in danger of being exceeded. Furthermore, the method may include using a combination of vacuum magnitude and duration measurements in a composite index or scale to indicate, through an output responsive to the value of the composite index or scale responsive to application of a vacuum to the fetus"" head, either safe use of the vacuum assisted delivery device or a potential for an injury-causing event if the vacuum is not released or relaxed.